In 12-inch nonstick skillet, heat remaining 2 tablespoons butter and 1 tablespoon of the vegetable oil. Cook 2 fish fillets at a time 4 to 6 minutes, turning once, until temperature in thickest part of fillet reads 145°F. Serve fish with aioli. To make tacos, fill tortillas with cooked fish and avocado; top with aioli and serve with lime wedges.